Patrol..replacing fuseable links with fuses, what size fuse?

[pongo]

in the process of replacing some wiring on a MK patrol and the fuse links are toast.

Using a fuse block with the large type of fuses from a falcon and all is good but am curious as to what size fuses i need to use.

I figure just add up whats running off each wire, etc and use that type of fuse. the new wiring would be good for excess amps so im guessing this method would be ok but would much rather use the exact fuse to use to stop a fire.

Thanks

[its aford not a nissan]

you might be better off using circut breakers as they will behave in a similar way to fuseable links

[GeneralFubashi]

agree, the original fusible links are designed to be able to carry above rated current for short periods of time before they melt. Normal fuses just blow once they hit their rating.

Put a couple of big breakers in where the links would have gone, and you can use normal fast blow fuses for all the other accessories. Breakers will also save you $ in fuses if you get the ratings wrong initially.

[pongo]

googled a bit and it looks like i used new style of fusible links and not fuses

here is a pic of the style im using.

[-Scott-]

agree, the original fusible links are designed to be able to carry above rated current for short periods of time before they melt. Normal fuses just blow once they hit their rating.

No. A fuse is intended to carry its rated current indefinitely (theoretically - don't expect it to work in reality.) Only a current over the rated current should cause it to blow, but the failure mechanism is heating of the fusible link to the point at which it physically falls apart.

A low level overload (e.g. 101% of rated current) will take longer to generate this heat (and therefore cause the fuse to fail) than a higher level overload (such as 500% of rated current.) The difference between fast blow/slow blow etc is how they respond to different levels of overload.

The fuse is there to protect the wire - the fuse should melt before the insulation on the wiring does. To replace your fusible link you need to find a rating for the wire it is protecting (suitably derated for a hot, underbonnet environment) and select a fuse/fusible link/breaker rated below this figure.

[GeneralFubashi]

wow, thanks for the correction, at rated/above rated: i never knew fuses were such precise components. But you are perfectly correct, and who needs practical advice when theory is unarguably correct.

[-Scott-]

What I was attempting to explain (after too many drinks) was that both fuses and fusible links will "carry above rated current for a short period of time."

The distinction you indicated is not correct - theoretically, or practically.

Perhaps you were attempting to say that fusible links will generally handle overloads better than fuses?

And yes, fuses can be very precise components. Selecting the correct fuse for a particular application can be a painful process for the inexperienced - like me.